Molded composite climbing structures utilizing selective localized reinforcement
A method and system for fabricating molded composite support members for use in climbing structures, which molded composite support members comprise variable performance properties along a longitudinal length thereof. The variable performance properties are achieved or provided by selectively reinforcing one or more regions determined to be subject to greater stress, thus allowing a minimum amount of material to be used in other areas that will subject to less structural stress. Selective reinforcement is accomplished by adapting one or more regions of a primary composite material composition with a supplemental composite material composition, wherein the supplemental composite material composition increases the amount of composite material fibers within that particular region.
This continuation in-part application claims the benefit of U.S. application Ser. No. 10/919,420, filed Aug. 16, 2004, and entitled, “Lightweight Composite Ladder Rail Having Supplemental Reinforcement in Regions Subject to Greater Structural Stress,” which is incorporated by reference in its entirety herein.
FIELD OF THE INVENTIONThis invention relates to various types of climbing structures, as well as to the support members used in the manufacture and/or assembly of such climbing structures, and more particularly to molded composite support members for use in climbing structures.
BACKGROUND OF THE INVENTION AND RELATED ARTClimbing structures, such as ladders, scaffolding, platforms, bleachers and others, in which a load (e.g., an individual or individuals, an object or objects, equipment, etc.) is intended to be supported are extremely common, and have found useful application in several different commercial settings and industries, in residential settings, and can be found virtually everywhere. The most common type of climbing structures are ladders and scaffolding, and types similar to these.
The use of portable ladders throughout history is well documented. Today, portable ladders are made not only of wood, but of aluminum alloys and composites using a variety of structural fibers.
Usually manufactured from spruce, wood ladders are relatively lightweight and inexpensive. As long as they are dry, they are safe for use around electricity. Wood ladders, though, have a number of drawbacks. Solid (i.e. non-laminated) pieces of wood used in the construction of ladders may have latent defects which can cause a structural failure. Wood is also subject to gradual, debilitating deterioration by moisture, sun, insects and microorganisms. Furthermore, expansion and contraction of wood caused by temperature and humidity changes can result in a gradual loosening of steps and braces, which requires frequent maintenance. Wood ladders also tend to be less stable in larger sizes.
Though aluminum alloys offer a high strength, lightweight alternative to wood, ladders made of aluminum alloys also have a number of drawbacks. Certain chemicals and salt water environments can corrode and weaken aluminum ladders. Although having excellent uniformity in the strength of structural members at the time of manufacture, the rails of aluminum ladders are easily bent and cracked. The most significant drawback is that aluminum is the third-best conducting metal. This attribute makes aluminum ladders extremely dangerous for work anywhere near high-voltage electrical wires. Historically, metal ladders have been the choice when electrical contact is not anticipated. Unfortunately, a ladder coming into contact with an electrical wire often occurs by accident. Therefore, a risk of electrocution may exist even when care is taken to avoid known and visible hazards. The problem is compounded because the light weight and high strength characteristics of metal ladders may be an inducement for their use even when electrical safety is a concern.
Though generally somewhat heavier and more expensive than aluminum ladders of the same size and rating, ladders having fiberglass composite rails joined with aluminum rungs have become extremely popular because they combine the best physical qualities of aluminum and wood ladders. The fiberglass composite rails will not conduct electricity. They are also very corrosion resistant. With minimal care and maintenance, fiberglass ladders can last generations.
Aluminum ladder rails are typically manufactured using an extrusion process. Fiberglass composite ladder rails, on the other hand, are typically manufactured using a pultrusion process. Pultrusion is a technique whereby longitudinally continuous fibrous materials are soaked in a resin bath and pulled through a heated die so that the resin sets and produces a rigid part downstream of the die. Both the extrusion process for aluminum rails and the pultrusion process for fiberglass composite rails produce rails of uniform cross section throughout their lengths.
The greatest weakness of the composite pultrusion and aluminum extrusion manufacturing processes is that the cross-sectional profile of the rail must remain constant throughout its entire length. During use, a ladder rail is subjected to different levels of stress, torque, shear, flex and abuse in different regions along its length. Therefore, if the rail needs more strength in a particular region, material must be added to the entire length of the rail. Thus, a ladder rail of uniform cross section throughout its length is necessarily overly strong and heavy throughout much of its length, while those regions subjected to maximum stress, torque, shear, flex and abuse are designed to be just strong enough to support the maximum rated load—plus an additional safety factor load—without failure, under expected usage conditions. Consequently, all ladders having rails of uniform cross section throughout their lengths are considerably heavier than they need to be. Neither the extrusion process nor the pultrusion process is readily adaptable to the manufacture of rails of non-uniform cross section over their lengths. This non-optimum condition has heretofore been considered acceptable in the interest of minimizing manufacturing costs. Although there has always been an effort to design air and water craft so that no portion of a aircraft, ship or boat is any stronger than it needs to be, in order to minimize unloaded weight and thereby maximize payload and/or performance of the craft, the concept has been largely ignored by manufacturers of ladders.
Today, the need for ladders that are light in weight and that can be safely handled by an individual working alone is of greater significance than the need for ladders which have a low initial purchase price. The purchase price is likely only a tiny fraction of the total costs related to treating and compensating potentially career-ending physical injuries sustained while carrying, loading, unloading, setting up, and taking down a conventional ladder over its useful life. This is especially true when the number of persons working in trades that require the frequent use of a portable ladder, who are nearing retirement age, who have either a small stature or a history of previous injuries related to the lifting and carrying of heavy objects, is taken into consideration. Utility workers, electricians, construction workers and telecommunication installers, in addition to homeowners and those in many other industries, could benefit from the availability of ladders, especially extension ladders, which are significantly lighter than those of the same ratings and sizes currently available.
With respect to scaffolding, platforms, bleachers, etc., several support members are typically interconnected with one another to form a lattice or matrix of support members for the purpose of supporting a surface in an elevated position, which surface may be used to support individuals, objects, equipment, or any other load. Similar to the current technology for ladder rails, scaffolding support members are typically constructed of aluminum, using an extrusion process and comprise a uniform cross-section. As a result, providing localized reinforcement in needed areas or regions only in order to minimize material in other areas or regions, thus saving weight and costs, has also largely been ignored by manufacturers of these types of climbing structures.
SUMMARY OF THE INVENTIONIn light of the problems and deficiencies inherent in the prior art, the present invention seeks to overcome these by providing a method and system for fabricating molded composite support members for use in climbing structures, which molded composite support members comprise variable performance properties along a longitudinal length thereof. The variable performance properties are achieved or provided by selectively reinforcing one or more regions determined to be subject to greater stress, thus allowing a minimum amount of material to be used in other areas that will subject to less structural stress. Selective reinforcement is accomplished by adapting one or more regions of a primary composite material composition with a supplemental composite material composition, wherein the supplemental composite material composition increases the amount of composite material fibers within that particular region.
In accordance with the invention as embodied and broadly described herein, the present invention resides in a climbing structure configured to support a load, the climbing structure comprising a surface operable to receive a load thereon; and at least one composite support member configured to support the surface, and having variable performance properties along a longitudinal length thereof, the composite support member comprising a primary composite material composition having an elongate, channel-shaped configuration; and a supplemental composite material composition operable to adapt selective regions of the primary composite material composition to provide selective localized reinforcement for facilitating and enhancing the variable performance properties.
The present invention also resides in a composite support member operable within a climbing structure, the composite support member comprising a primary composite material composition having an elongate, channel-shaped configuration, and comprising material fibers oriented on a zero degree angle with respect to a longitudinal axis of the support member; and a supplemental composite material composition operable to selectively reinforce the primary composite material composition and to facilitate variable performance properties of the support member along a longitudinal length thereof, the supplemental composite material composition comprising a plurality of composite material fibers oriented to enhance the performance properties.
The present invention also resides in a composite support member for use within a climbing structure, the composite support member comprising a primary composite material composition having an elongate, channel-shaped configuration; and a supplemental composite material composition operable to adapt the primary composite material composition along substantially an entire length thereof, to provide reinforcement for facilitating and enhancing one or more performance properties of the primary composite material composition, the primary composite material composition and the supplemental composite material composition configured to provide a uniform cross-sectional area along a longitudinal length of the support member.
The present invention further resides in a method for fabricating a composite support member operable within a climbing structure, the method comprising preparing a primary composite material composition having an elongate, channel-shaped configuration; preparing a supplemental composite material composition; adapting a region of the primary composite material composition with the supplemental composite material composition to provide selective localized reinforcement of the primary composite material composition, and to form the composite support member, the supplemental composite material facilitating variable performance properties along a longitudinal length of the support member.
The present invention still further resides in a method for providing a climbing structure, the method comprising obtaining first and second composite support members, each having variable performance properties along a longitudinal length thereof provided by adapting a region of a primary composite material composition with a supplemental composite material composition to provide selective localized reinforcement of the primary composite material composition; and interconnecting the first and second composite support members to form at least a portion of the climbing structure.
BRIEF DESCRIPTION OF THE DRAWINGSThe present invention will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings merely depict exemplary embodiments of the present invention they are, therefore, not to be considered limiting of its scope. It will be readily appreciated that the components of the present invention, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Nonetheless, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
The following detailed description of exemplary embodiments of the invention makes reference to the accompanying drawings, which form a part hereof and in which are shown, by way of illustration, exemplary embodiments in which the invention may be practiced. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be realized and that various changes to the invention may be made without departing from the spirit and scope of the present invention. Thus, the following more detailed description of the embodiments of the present invention is not intended to limit the scope of the invention, as claimed, but is presented for purposes of illustration only and not limitation to describe the features and characteristics of the present invention, to set forth the best mode of operation of the invention, and to sufficiently enable one skilled in the art to practice the invention. Accordingly, the scope of the present invention is to be defined solely by the appended claims. The following detailed description and exemplary embodiments of the invention will be best understood by reference to the accompanying drawings, wherein the elements and features of the invention are designated by numerals throughout.
The present invention describes a method and system for fabricating molded composite support members for use in climbing structures, which molded composite support members comprise variable performance properties along a longitudinal length thereof. The variable performance properties are achieved or provided by selectively reinforcing one or more regions determined to be subject to greater stress, thus allowing a minimum amount of material to be used in other areas that will subject to less structural stress. Selective reinforcement is accomplished by adapting one or more regions of a primary composite material composition with a supplemental composite material composition, wherein the supplemental composite material composition increases the amount of composite material fibers within that particular region.
Advantageously, select regions may comprise supplemental composite material fibers without being constrained by the manufacturing process used to fabricate the support members. In other words, any region or area of a support member that may be subject to increased loading or stress may comprise supplemental reinforcement simply by increasing the number of material fibers in that region, wherein one or more composite manufacturing processes may be employed to either couple or consolidate such material fibers. In addition, select portions of a select region, or select portions of the support member, may be reinforced without having to reinforce unnecessary areas, thus allowing a greater optimization of strength to weight ratio, or allowing the performance properties to be enhanced and optimized while keeping weight and costs to a minimum. With the concepts discussed herein, composite support members for use in climbing structures may be fabricated having either uniform or non-uniform cross-sections.
The present invention provides several other significant advantages over prior related climbing structures and support members operable to provide a climbing structure, some of which are recited here and throughout the following more detailed description. First, the support members are comprised of a composite material capable of being molded, and therefore take advantage of the various techniques for fabricating composites. Second, reinforcement of the support members may be accomplished by reinforcing only select areas or regions of the support member, thus permitting the performance properties of the support member to be optimized, while also allowing weight to be kept at a minimum. Third, both uniform and non-uniform cross-sections are made possible, depending upon the type of method used to create the support member, and the application in which the support member is intended for use. Fourth, composite material fibers of different orientation may be used in reinforced areas or regions to secure other composite material fibers, thus eliminating the need to provide a separate fiber material or mat to secure the composite material fibers. Fifth, selective reinforcement in localized areas may be accomplished using a supplemental composite material composition, having composite material fibers therein, wherein the supplemental composition may be consolidated with a primary composite material composition (e.g., integrally formed with) at a desired location or area, or that may be formed and provided independently or separately (e.g., in the form of a clamp-on sleeve) and then removably coupled to a desired region or area. Sixth, different types of composite materials (e.g., thermoplastics, thermosets) may be used, along with different manufacturing methods (e.g., resin transfer molding, vacuum assisted resin transfer molding, compression molding, bladder molding, etc.), to create an optimal support member for use in a climbing structure.
Each of the above-recited advantages will be apparent in light of the detailed description set forth below, with reference to the accompanying drawings. These recited advantages are not meant to be limiting in any way. Indeed, one skilled in the art will appreciate that other advantages may be realized, other than those specifically recited herein, upon practicing the present invention.
The term “climbing structure,” as used herein, shall be understood to mean any type of structure utilized in one or more industries, wherein the climbing structure is configured to support a load from one or more individuals and/or one or more objects or items. As used herein, climbing structures are intended to comprise at least one composite support members, as defined and discussed herein. Examples of contemplated climbing structures include, but are not limited to, ladders, scaffolding, platforms, bleachers, planks utilized in scaffolding or platforms, and others known in the art.
The term “composite support member” or “support member,” as used herein, shall be understood to mean a molded composite structural support component utilized to assemble, fabricate and/or otherwise form part of a climbing structure. The composite support member may comprise primary composite material fibers, as well as one or more supplemental composite material fibers intended to reinforce the support member in selective regions or along selective locations. In addition, the composite support member may comprise a thermoplastic or thermoset type of composite. Exemplary types of composite support members may include, but are not limited to, ladder rails, individual interconnecting support members used in assembling scaffolding, platforms, bleachers, etc., and others known in the art.
The term “performance properties,” as used herein, shall be understood to mean those inherent properties of the climbing device, such as stiffness, strength, torsional resistance, dielectric or insulating capabilities, and others.
The term “channel-shaped structure” or “channel shape,” as used herein, shall be understood to mean a structure having opposing flange portions extending upward from a back or web to form a channel. The composite support member described herein comprises at least one channel, but may comprise others. Exemplary channel shapes include a U-shaped structure, a C-shaped structure, an I-shaped structure, a V-shaped structure (with no back or web), flanges that initially extend upward from the web or back on an incline or curve, and then transition into perpendicular flanges, and others as will be recognized by those skilled in the art.
The term “composite material composition,” as used herein, shall be understood to mean a composite component used in the fabrication of a composite support member. The composite material composition comprises fibers or composite fiber materials as known in the art. The composite material composition may comprise any number of fibers or layers of fiber materials. In addition, the composite material composition may comprise fibers oriented on a zero degree angle with respect to a longitudinal axis, fibers oriented transverse to the longitudinal axis, or both of these in various ratios.
To fabricate the molded composite support members of the present invention, structural composite fibers of many types may be used. Use of the following fibers is presently contemplated-glass (types E, S, S2, A or C), quartz, poly p-phenylene-2,6-bezobisoxazole (PBO), basalt, boron, aramid fibers such as Nomex® and Kevlar® (poly-para-phenylene terephthalamide), ultra-high-molecular-weight polyethylene, carbon, graphite and fiber hybrids such as carbon/aramid and carbon/glass. For climbing structures used near electrical circuits, support members having non-conductive fibers may be mandatory. Type E glass fibers have excellent dielectric properties and are the most commonly used structural fiber. However type S and S2 glass fibers have greater strength. Quartz fibers, while more expensive than glass, have lower density, higher strength and higher stiffness than E-glass, and about twice the elongation-to-break ratio, making them an excellent choice where durability is of paramount importance. Boron fibers, which are five times as strong, twice as stiff as steel, and non-conductive, are also ideal for structural fiber reinforcement of support members for use in climbing structures.
A discussion of resin matrices is also in order, as the present invention composite climbing structures, and particularly the support members utilized in these structures, may be implemented using a variety of different resin matrices. There are basically two kinds of polymeric resins, namely thermosetting and thermoplastic or thermoform resins. Certain types of resins are available in both formulations.
Unsaturated polyester resins are extensively used because of their ease of handling, good balance of mechanical, electrical and chemical properties, and relatively low cost. Typically used in combination with glass fiber reinforcements, polyester resins are most commonly used in compression molding and resin transfer molding. Several basic types of polyester resins are available, including orthopolyester resins, isopolyester resins and terephthalic polyester resins, with the latter type exhibiting increased toughness. Vinyl ester resins provide enhanced performance, as compared with polyester resins, but at additional cost. However, vinyl ester resins do not match the performance of high-performance epoxy resins. For advanced composite matrices, the most common thermosetting resins are epoxies, phenolics, cyanate esters, bismaleimides (BMIs), and polyimides. Most commercial epoxies have a chemical structure based on the diglycidy ether of bisphenol A or creosol and/or phenolic novolacs. Phenolics are based on a combination of an aromatic alcohol and an aldehyde, such as phenol combined with formaldehyde. Phenolics are relatively inexpensive and have excellent flame-resistance and heat absorption properties. Cyanate esters are high in strength and toughness, absorb little moisture, and are excellent dielectrics. Bismaleimides and polyimide resins are used in high-temperature applications. Polybutadiene resins are excellent dielectrics, resistant to chemicals, and may be used in many applications as an alternative to expoxy resins. Polyethermide thermoset resins, which are derived form bisoxazolines and formaldehyde-free phenolic novolacs, are a cost-effective alternative to eepoxy and bismaleimide resins.
A non-exhaustive list of commodity thermoplastic resins includes polyethylene (PE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC), acrylonitrile butadiene acrylate (ABS), polyamide (PA or nylon), and polypropylene (PP). High-performance thermoplastic resins, such as polyetheretherketone (PEEK), polyetherketone (PEK), polyamide-imide (PAI), polyarylsufone (PAS), polyetherimide (PEI), polyethersulfone (PES), polyphenylene sulfide (PPS) and liquid crystal polymer (LCP), withstand high temperatures, do not degrade when exposed to moisture, and provide exceptional impact resistance and vibration dampening. These characteristics make them useful for the manufacture of composite climbing structures.
Cyclic thermoplastic polyester has excellent fiber wetting characteristics and offers the properties of a thermoplastic and the processing features of a thermoset.
Both polyimide and polyurethane resins are available in both thermoset and thermoplastic formulations.
Unlike many prior related climbing structures having support members manufactured using a pultrusion or similar process, the present invention employs a composite molding process to manufacture the one or more composite support members configured for use in a climbing structure, including those having one or more strategically structurally reinforced regions. Such molding processes include, but are not limited to high-pressure injection molding, resin-impregnated fiber molding, compression molding, resin transfer molding (RTM), using rigid closed mold or a combination hard and soft mold, vacuum-assisted resin transfer molding (VARTM) using a rigid or flexible cover over a one-sided mold, and various bladder molding processes in which a bladder and mandrel operate to form the support members within a mold cavity, many of which are well known in the art. Each of these is discussed in some detail below.
Using high-pressure injection molding, a structural preform is placed in a mold cavity, the mold closed, and a bulk molding compound, which may be a molten thermoplastic resin or uncured thermoset resin, is injected into the mold cavity under high pressure, completely wetting the preform and assuming the shape of the mold cavity. After the injected material cools (in the case of the thermoplastic resin) or cures (in the case of the thermoset resin) and solidifies, the completed part can be removed from the mold cavity.
Using resin-impregnated fiber molding, a controlled amount of thermoset or thermoplastic resin is incorporated into resin-impregnated structural fiber form (commonly called prepregs) using solvent, hot-melt or powder impregnation technologies. Prepregs can be stored in an uncured state until used. The prepreg structural preform is placed in a precision closed mold and subjected to heat and pressure. In the case of thermoplastic resin, the resin in the preform melts, wetting the structural fibers. The melted resin fibers or particles assume the shape of the mold. After cooling or curing, a finished part is removed from the mold. In the case of a thermoset prepreg part, the preform is stored in a refrigerator until it is cured in a heated precision closed mold.
Using compression molding, structural fiber layer is sandwiched between two layers of thick resin paste to form a sheet molding compound. A piece of the sheet molding compound is placed in a heated closed mold to which 500 to 1,200 psi of pressure is applied. Material viscosity drops and the sheet molding compound flows to fill the mold cavity. After cure, the mold is opened and the part removed. Though the compression molding process typically uses thermoset resins, it can also be used with thermoplastic resins.
Resin transfer molding (RTM), using a closed mold, is presently considered to be one of the preferred molding methods for quantity production of support members for climbing structures produced in accordance with the present invention. With RTM, both parts of a two-part, matched, closed mold are fabricated from metal or composite material. Alternatively, one part of a two-part compression mold is fabricated from metal or composite material, and a second part is fabricated from a compressible rubber material. After the dry fibers are placed in the mold, the mold is closed and the resin is then injected into the mold to wet the fibers and fill the mold. For thermoset resins, the mold can be heated to accelerate curing of the part, although that is not necessarily required if curing of the resin has been chemically initiated. For thermoplastic resins which are injected as a molten liquid, the injected material is simply allowed to cool to solidify after coating the fibers and filling the mold.
With vacuum assisted resin transfer molding, fiber reinforcements are placed in a one-sided mold and a cover, which may be either rigid or flexible, is placed over the top of the mold to form a vacuum-tight seal. When using a flexible cover, which is typically an air impermeable bag (e.g., a vacuum bag), the flexible cover essentially forms the other side of the mold. Catalyzed resin is typically introduced through strategically located ports on one side of the mold, and a partial vacuum is applied to ports located on the other side thereof. The partial vacuum extracts the air and pulls the resin through the preform to create the part. Once the resin sets up, the completed part is removed from the mold. Polyester, two-part epoxy, bismaleimide and polyetheramide resins are commonly used in the RTM and VARTM processes.
Within a bladder molding process, a mandrel/bladder assembly is provided that is operable to conform a composite preform to one or more walls of a mold cavity of a mold. The mandrel/bladder assembly may comprise a mandrel sized and configured to fit within the mold cavity, and to define, at least in part, a volume of space between the mandrel and the preform, each as positioned within the mold cavity. The mandrel/bladder assembly further comprises an actuatable bladder supported about at least a portion of and operable with the mandrel, and which is configured to fill the volume of space upon being actuated to cause the preform to conform to the mold cavity. The mandrel/bladder assembly is operable with a bladder molding system comprising various support components, heaters, etc. to fabricate a finished composite article, such as a composite climbing structure as described herein. Exemplary bladder molding processes particularly useful in fabricating the climbing structures described herein are set forth in copending U.S. Provisional Application No. ______, filed Feb. 16, 2007, and entitled, “Bladder Molding Systems and Methods for Fabricating Composite Articles” (Attorney Docket No. 2384-003), which is incorporated by reference in its entirety herein.
As indicated above, the present invention contemplates several different types of climbing structures that may be fabricated in accordance with the teachings as described and set forth herein. With the reference to
It is understood that support members, other than ladder rails, may comprise a similar configuration and makeup. As such, each of the different types are not specifically described herein. However, one skilled in the art will be able to recognize that the teachings of a support member in the form of a ladder rail for use in a ladder-type climbing structure, wherein the ladder rail incorporates variable performance properties through reinforcement along its longitudinal length, as described herein, may be applicable to the fabrication of support members of different types for use in different climbing structures, such as scaffolding. As such, the specific discussion of ladder rails presented herein is not meant to be limiting in any way.
It is also to be understood that the drawing FIGS. are merely illustrative of exemplary ladder rails and processes used to manufacture or fabricate these. In essence, it is contemplated that a composite ladder rail may be supplementally reinforced in strategic locations in one or more longitudinal regions, for a variety of applications, by increasing the number of structural fibers in those regions, resulting in a corresponding increase in the thickness of the rail and its cross-sectional area in the structurally-reinforced regions. The technique of supplemental reinforcement in strategic locations about the composite support member, or ladder rail, can be applied to ladder rails of different types intended for use in ladders of different types and intended for a variety of applications. Such ladders may include, but are not limited to, self-supporting step ladders, non-self-supporting extension ladders, and combination ladders.
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By incorporating four second embodiment rails 601 into the fly sections of the combination ladder of the '055 patent, the weight thereof can be substantially reduced. Still referring to
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The ladder rail 601 may further comprise a veil layer 901 of finely woven cotton/polyester cloth to encapsulate the structural fiber layers and minimize the problem of fiberglass segments projecting through the surface of the rail. The transitions 801 and 802 within the rail back 606 wrap upwardly from the rail back 706 to the rail flanges 604A and 604B.
It should be understood that the multi-layered preform of
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The flange recesses 1602A and 1602B are completely visible, with the distance D1 between the outer wall 1603 of flange recess 1602A and the outer wall 1604, of flange recess 1602B remaining constant over the entire length of the mold. The distance between the inner wall 1605 of flange recess 1602A and the inner wall 1606 of flange recess 1602B, on the other hand, varies from a maximum D2 in region 1607, where the flanges are thinnest to a minimum D4 in region 1609, where the flanges are thickest. In region 1608, the distance D3 is an intermediate value. The rail back surface mold surface 1610 of the mold cavity portion 1003 of mold 1001, which sculpts the inner surface of the rail back, is divided into three regions of different levels. Region 1610A is nearest the viewer, region 1610C is farthest from the viewer, and region 1610B is positioned at an intermediate distance from the viewer. It will be noted that there are also ramps 1610D and 1610E between the different levels of the rail base 1610 mold surface. It will also be noted that the transition regions 1611A, 1611B, 1611C and 1611D between regions of different levels for the rail flange recesses 1602A and 1602B are ramped, rather than abrupt, in order to reduce stresses at the transition region.
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It should be apparent that a composite ladder rail may be fabricated in accordance with the present invention for use with a folding step ladder. U.S. Pat. No. 4,718,518 to William E. Brown (the '518 patent) discloses one convertible step ladder having a two-piece back section. This patent is hereby also incorporated by reference into the present application. A lower piece of the back section is removable so that the step ladder can be used on stairs as well as on a flat surface. Composite or fiberglass rails may be molded in accordance with the present invention for use with either a conventional step ladder having a one-piece back section or for a convertible step ladder. The rails may be reinforced in appropriate locations, such as the foot of the rail, the top of the rail where it is hinged, or an attachment region for a removable lower piece of the back section.
It should be understood that different types of steps may be incorporated into any of the types of ladders discussed herein. Various methods for attaching steps to the rails may also be used. For example, the step may be swedged or welded to a bracket which is attached with rivets or screws to the rail. Alternatively, a hole may be cut or stamped in the rail, and an end of the step inserted within the hold and held in place with swedged retaining rings. The types of steps to be used and the method of their attachment to the rail fall largely outside the scope of this disclosure, as many types of steps and many methods of step-to-rail attachments are well known in the art and may be applied to the art of ladder manufacture using the rails of the present invention. That is to say that the practice of the present invention is not limited to any particular type of step or any particular method of step-to-rail attachment.
It should also be evident that the preforms used to make the rails of the present invention may be completely formed prior to their insertion in the mold, or they may be constructed by laying up multiple layers, which may even be done manually within the mold.
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In this particular embodiment, the primary and supplemental composite material compositions 2126 and 2130, respectively, are intended to be shown as being consolidated or integrally formed with one another to form a unitary flange, or a unitary support member. This is accomplished in an initial fabrication process, or in a subsequent process, such as a remold process.
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With reference to FIGS. 22-A and 22-B, illustrated is a partial perspective and a cross-section view, respectively, of a molded composite support member, in the form of a ladder rail, formed in accordance with another exemplary embodiment of the present invention. As shown, the ladder rail 2210 comprises a first flange 2214 and a second flange 2218 opposite one another and extending upward from a web or flange back 2222. The composite ladder rail 2210 is configured to comprise variable performance properties along a longitudinal length thereof provided by adapting a region 2238 of a primary composite material composition, shown as composition 2226 with a supplemental composite material composition, shown as composition 2230, to provide selective localized reinforcement of the primary composite material composition 2226.
In this particular embodiment, the primary and supplemental composite material compositions 2226 and 2230, respectively, are independent of one another, or in other words they are not integrally formed or consolidated with one another. Rather, the supplemental composite material composition 2230 comprises composite material fibers that are configured as and that reside within a sleeve 2242, which sleeve 2242 is formed independent of the primary composite material composition 2226. The sleeve 2242 is configured to be removably coupled to the primary composite material composition 2226 using any known means in the art, such as bolting, clamp-on, and others. In the exemplary embodiment shown, the sleeve 2242 is shown as comprising a clamp-on coupling means utilizing an interference fit. In addition, the sleeve 2242 is shown as providing reinforcement to both the first and second flanges 2214 and 2218, respectively, as well as the web or flange back 2222.
The sleeve 2242 is shown as further comprising a tapering portion 2246 configured to provide a smooth transition from the sleeve 2242 to the primary composite material composition 2226. The tapering portion 2246 further functions to more evenly distribute loads about the primary composite material composition 2226, and to reduce the concentration and localization of forces within a given area so as to eliminate local weak spots.
With reference to FIGS. 23-A and 23-B, illustrated is a partial perspective view and a cross-section, respectively, of a molded composite support member, in the form of a ladder rail, formed in accordance with another exemplary embodiment of the present invention. As shown, the ladder rail 2310 comprises a first flange 2314 and a second flange 2318 opposite one another and extending upward from a web or flange back 2322. Unlike the composite ladder rails discussed above that are configured to comprise variable performance properties along a longitudinal length thereof, ladder rail 2310 is configured to comprise more consistent or constant performance properties along its longitudinal length. Reinforcement of the ladder rail 2310 is provided by adapting, along an entire length of a primary composite material composition, shown as composition 2326, with a supplemental composite material composition, shown as composition 2330-a and 2330-b, to provide continual reinforcement of the primary composite material composition 2326 in a longitudinal direction.
As can be seen, the ladder rail 2310 comprises a uniform cross-section having a superior strength to weight ratio and superior performance properties over prior related ladder rails having a uniform cross-section. This is primarily the case as the web or flange back 2322 is not required to comprise added material, thus allowing its thickness tw to be less than the thickness tf of the first and second flanges 2314 and 2318. In one aspect, the supplemental composite material compositions 2330-a and 2330-b may be configured to extend about a surface of the flanges 2314 and 2318, respectively, terminating at or prior to the intersection or junction of the flanges and the web or flange back 2322. However, in another preferred aspect, the supplemental composite material compositions 2330-a and 2330-b are configured to be positioned and extend about a surface of the flanges 2314 and 2318, respectively, and at least partially about a surface of the web or flange back 2322, through the intersection or junction of the flanges and the web or flange back to reinforce this intersection or junction. By extending through the intersection, a radius r of increased strength is provided, thus improving the overall strength and stiffness of the ladder rail 2310.
With reference to
For example, within a combination of material fibers oriented in different directions, the ratio of material fibers oriented on a zero degree angle with respect to those transversely oriented may vary. Specifically, the percentage of material fibers oriented on a zero degree angle may range between 70 and 95 percent of the total fiber content of the support member, with the percentage of material fibers oriented transverse to the longitudinal axis ranging between 5 and 30 percent of the total fiber content of the support member. Orientations of fiber content in these ranges has been found to provide optimal results in fabricated support members, namely to keep weight and manufacturing costs to a minimum without sacrificing desired performance properties. The function of the different fiber orientations is discussed below.
With reference to
One or both of the primary composite material composition 2426 and the supplemental composite material composition 2430-c are intended to comprise a percentage of transversely oriented material fibers for the purpose of securing the opposing sides or flanges 2414 and 2418 of the ladder rail 2410 together. By securing opposing sides of the ladder rail together with material fibers oriented transverse to the longitudinal axis of the ladder rail, improved performance properties are realized. Again, a discussion on material fiber orientation and the relationship of these to the performance properties of the support member is provided below.
With reference to
A relatively flat platen 2562 may be situated above the beams, which platen functions as a support on which a mold 2554 having a mold cavity 2558 may rest. In other words, the platen 2562 provides a working surface. The platen 2562 and the mold 2554 may be any size and configuration as needed.
The beams may be affixed atop a plurality of support legs (not shown), which would function to bring the working surface to a comfortable height. Below the beams may be one or more pneumatic cylinders (not shown), which move in unison a clamping mechanism (not shown) that secures a mandrel/bladder assembly 2566 in place during the pressure cycle.
Using a lengthwise clamp (not shown), the mandrel/bladder assembly 2566 may be clamped along its entire length, eliminating the need for a large structure to withstand the loads the mandrel/bladder assembly 2566 will exert while under pressure.
A series of electric infrared heaters 2582 may be assembled and supported on a moveable unit (not shown) that is itself supported on a track (not shown), thus allowing the heaters to be positioned in place directly over the mold during the heating cycle, and then subsequently retracted out the way of the mandrel/bladder assembly 2566 during the pressure, loading, and unloading cycles.
The mandrel/bladder assembly 2566 may be constructed of an aluminum frame of sufficient strength to handle the molding pressure while being held by the clamps. Below the aluminum frame may be a hollow aluminum rectangular extrusion member (e.g., one off the shelf) which functions as the mandrel 2570, initiating the forming of the preform by pressing it into the mold cavity 2558 and folding the primary and supplemental composite material components upward.
The extrusion member or mandrel 2570 may be encased in a resilient, airtight membrane or bladder 2574. The resilient membrane or bladder 2574 may comprise a tube shape to match the aluminum extrusion member or mandrel 2570. In one aspect, as discussed above, the bladder 2574 is supported about only the bottom and side surfaces of the mandrel 2570, with the top of the mandrel 2570 being left exposed. In this respect, the top surface of the mandrel 2570 may come in contact and interface with a mold top 2578 used to enclose the cavity 2558 of the mold 2554. The mandrel 2570 serves as an air distribution manifold for delivering high pressure air into the resilient membrane or bladder 2574 quickly and evenly along its length one or more through holes drilled at regular intervals.
The mandrel/bladder assembly 2566 facilitates the process of forming the composite support member 2510, and particularly the preform of the primary composite support material composition 2526 and the various supplemental compositions 2530-a, 2530-b, and 2530-c, within the mold cavity 2558. It is noted that the primary and supplemental compositions may be consolidated together under pressure and heat to form a single unitary preform ready to be inserted into the mold 2554. The mandrel/bladder assembly 2566 facilitates initiation of the forming process and induces the needed molding pressure. The mandrel/bladder assembly 2566, retractable heaters 2582, and lengthwise clamp are all operable together to provide the advantages of the present invention.
With reference to
With respect to the material fibers, the performance properties of the composite support member are largely determined by the orientation and number of composite material fibers making up the support member. Along the longitudinal length of the support member, the total fiber content will typically comprise more fibers oriented on a zero degree angle with respect to a longitudinal axis of the support member. However, there may also be present material fibers oriented transverse to this longitudinal axis, namely material fibers oriented on an angle between 45 and 90 degrees, and preferably between 60 and 90 degrees, with fibers oriented on ninety degree angles being specifically preferred as these will provide the greatest enhancement and efficiency of strength, stiffness and other desirable properties. Material fibers oriented on angles less than 90°, but yet greater than 0°, will still provide somewhat of an increase or enhancement of strength and stiffness and other properties, but this will most likely be less than that achieved by using material fibers oriented on 90° angles.
Although the present invention contemplates a single composite support member comprising all longitudinally oriented material fibers (such as the ladder rail described in
For a support member having optimized performance properties, it has been discovered that the total material fiber content of the support member will preferably comprise between 5 and 30 percent transversely oriented material fibers, and between 70 and 95 percent longitudinally oriented material fibers. In other words, support members for use in climbing structures may be optimized by providing at least some material fibers that are oriented transversely to the several longitudinally oriented material fibers. However, there will generally be more longitudinally oriented material fibers than transversely oriented material fibers.
Climbing structures may be subject to various industry standards, such as commonly known ANSI standards. ANSI provides tests for climbing structures in order to rate their performance and to see if they can perform within the set standards. In the example of a ladder, ANSI states that in order to achieve an acceptable rating, the ladder can only deflect a certain amount or distance under a given load. In addition, the ladder must meet a strength test, which is a failure test, wherein the ladder is required to hold a given load until failure. There are also various incline tests, torque tests, foot braking tests, and others. The results of these tests are directly affected by the number, relationship and orientation of respective material fibers present within the ladder rails making up the ladder.
With reference to
Again, the above description pertaining to molded composite support members in the form of molded composite ladder rails is not intended to be limiting in any way, as the techniques and concepts described above and set forth in the drawings is intended to be applicable to the manufacture of other types of molded composite support members for use in other types of climbing structures.
The foregoing detailed description describes the invention with reference to specific exemplary embodiments. However, it will be appreciated that various modifications and changes can be made without departing from the scope of the present invention as set forth in the appended claims.
The detailed description and accompanying drawings are to be regarded as merely illustrative, rather than as restrictive, and all such modifications or changes, if any, are intended to fall within the scope of the present invention as described and set forth herein. More specifically, while illustrative exemplary embodiments of the invention have been described herein, the present invention is not limited to these embodiments, but includes any and all embodiments having modifications, omissions, combinations (e.g., of aspects across various embodiments), adaptations and/or alterations as would be appreciated by those in the art based on the foregoing detailed description. The limitations in the claims are to be interpreted broadly based on the language employed in the claims and not limited to examples described in the foregoing detailed description or during the prosecution of the application, which examples are to be construed as non-exclusive. For example, in the present disclosure, the term “preferably” is non-exclusive where it is intended to mean “preferably, but not limited to.” Any steps recited in any method or process claims may be executed in any order and are not limited to the order presented in the claims. Means-plus-function or step-plus-function limitations will only be employed where for a specific claim limitation all of the following conditions are present in that limitation: a) “means for” or “step for” is expressly recited; and b) a corresponding function is expressly recited. The structure, material or acts that support the means-plus function are expressly recited in the description herein. Accordingly, the scope of the invention should be determined solely by the appended claims and their legal equivalents, rather than by the descriptions and examples given above.
Claims
1. A climbing structure configured to support a load, said climbing structure comprising:
- a surface operable to receive a load thereon; and
- at least one composite support member configured to support said surface, and having variable performance properties along a longitudinal length thereof, said composite support member comprising: a primary composite material composition having an elongate, channel-shaped configuration; and a supplemental composite material composition operable to adapt selective regions of said primary composite material composition to provide selective localized reinforcement for facilitating and enhancing said variable performance properties.
2. The climbing structure of claim 1, wherein said supplemental composite material composition is operable to adapt selective regions of said primary composite material composition in a longitudinal direction.
3. The climbing structure of claim 1, wherein said composite support member comprises opposing flanges extending upward to define a channel of said channel-shaped configuration.
4. The climbing structure of claim 1, further comprising first and second composite support members interconnected to one another to support said surface and said load.
5. The climbing structure of claim 1, wherein said composite support member is used to construct a climbing structure of the type selected from the group consisting of a ladder, scaffolding, a platform, a display, a plank, and bleachers.
6. A composite support member operable within a climbing structure, said composite support member comprising:
- a primary composite material composition having an elongate, channel-shaped configuration, and comprising material fibers oriented on a zero degree angle with respect to a longitudinal axis of said support member; and
- a supplemental composite material composition operable to selectively reinforce said primary composite material composition and to facilitate variable performance properties of said support member along a longitudinal length thereof, said supplemental composite material composition comprising a plurality of composite material fibers oriented to enhance said performance properties.
7. The composite support member of claim 6, wherein said primary composite material composition comprises material fibers oriented transverse to said longitudinal axis to increase the performance properties of said primary composite material composition.
8. The composite support member of claim 6, wherein said support member comprises opposing flanges extending upward to define a channel of said channel-shaped configuration.
9. The composite support member of claim 8, wherein said supplemental composite composition is positioned and extends about a surface of said opposing flanges and partially about said web, through an intersection of said flanges and said web, thus reinforcing said intersection.
10. The composite support member of claim 6, wherein said supplemental composite material operates to only reinforce said opposing flanges, thus eliminating a need for reinforcing any web or back portions of said primary composite material composition.
11. The composite support member of claim 6, wherein said material fibers of said supplemental composite material composition are all oriented on a zero degree angle with respect to said longitudinal axis, and are used to reinforce the material fibers of the primary composite material composition, also oriented on a zero degree angle with respect to said longitudinal axis.
12. The composite support member of claim 6, wherein at least a portion of said material fibers of said supplemental composite material composition are oriented on a zero degree angle with respect to said longitudinal axis, and wherein at least a portion of said material fibers of said supplemental composite material composition are oriented transverse to said longitudinal axis in order to optimize and/or enhance a strength to weight ratio, and to increase stiffness of said support member.
13. The composite support member of claim 12, wherein between 5 and 30 percent of said material fibers present within said supplemental composite material composition are oriented transverse to said longitudinal axis, and wherein between 70 and 95 percent of said material fibers present within said supplemental composite material composition are oriented on a zero degree angle with respect to said longitudinal axis, said percentages being based on a total material fiber content.
14. The composite support member of claim 12, wherein said material fibers of said supplemental composite material composition oriented transverse to said longitudinal axis are oriented on an angle between 45 and 90 degrees with respect to said longitudinal axis.
15. The composite support member of claim 12, wherein at least a portion of said material fibers of said primary composite material composition oriented on a zero degree angle with respect to said longitudinal axis are operably secured together by at least a portion of said material fibers of said supplemental composite material composition oriented transverse to said longitudinal axis.
16. The composite support member of claim 12, wherein at least a portion of said material fibers of said primary composite material composition oriented on a zero degree angle with respect to said longitudinal axis are operably secured together by at least a portion of material fibers, also within said primary composite material composition, oriented transverse to said longitudinal axis.
17. The composite support member of claim 6, wherein said supplemental composite material composition resides in and forms a sleeve configured to be selectively and removably coupled to said primary composite material composition to provide localized reinforcement to said primary composite material composition and said support member, said sleeve not being integrally formed with and comprising a material composition independent of said primary composite material composition.
18. The composite support member of claim 6, wherein said supplemental composite material composition is consolidated with said primary composite material composition to comprise an integrally formed unitary composite material composition.
19. The composite support member of claim 18, wherein said primary and supplemental composite material compositions are of a thermoplastic type, and wherein said supplemental composite material composition is remolded together with said primary composite material composition to effectuate integral consolidation of said primary and secondary composite material compositions.
20. The composite support member of claim 6, wherein said supplemental composite material composition spans substantially an entire length of said support member to maintain a uniform cross-sectional area as taken laterally across said longitudinal axis of said support member.
21. The composite support member of clam 6, wherein said supplemental composite material composition is located in select regions of said support member to be reinforced, thus providing a non-uniform cross-sectional area as taken laterally across said longitudinal axis of said support member.
22. The composite support member of claim 6, wherein said supplemental composite material composition tapers along its length to more evenly distribute loads across said primary composite material composition, and to reduce the concentration and localization of forces within a given area.
23. The composite support member of claim 6, wherein said primary and supplemental composite material compositions comprise a thermoplastic makeup.
24. A composite support member for use within a climbing structure, said composite support member comprising:
- a primary composite material composition having an elongate, channel-shaped configuration; and
- a supplemental composite material composition operable to adapt said primary composite material composition along substantially an entire length thereof, to provide reinforcement for facilitating and enhancing one or more performance properties of said primary composite material composition,
- said primary composite material composition and said supplemental composite material composition configured to provide a uniform cross-sectional area along a longitudinal length of said support member.
25. The composite support member of claim 24, wherein said support member comprises opposing first and second flanges extending upward from a web, said flange portions having a reinforced increased thickness with respect to a thickness of a majority of said web.
26. The composite support member of claim 25, wherein said supplemental composite composition extends about said first and second flanges and partially about said web, through an intersection of said first and second flanges and said web, thus reinforcing said intersection.
27. A method for fabricating a composite support member operable within a climbing structure, said method comprising:
- preparing a primary composite material composition having an elongate, channel-shaped configuration;
- preparing a supplemental composite material composition; and
- adapting a region of said primary composite material composition with said supplemental composite material composition to provide selective localized reinforcement of said primary composite material composition, and to form said composite support member, said supplemental composite material facilitating variable performance properties along a longitudinal length of said support member.
28. The method of claim 27, wherein said preparing a supplemental composite material composition comprises preparing a sleeve configured to be selectively and removably coupled to said primary composite material composition to provide said localized reinforcement of said primary composite material composition, said sleeve being and comprising a material composition independent of said primary composite material composition.
29. The method of claim 27, wherein said adapting comprises consolidating said supplemental composite material composition with said primary composite material composition to comprise an integrally formed unitary composite material composition.
30. The method of claim 29, wherein said supplemental composite material composition is remolded together with said primary composite material composition to achieve said consolidating of said supplemental composite material composition with said primary composite material composition.
31. The method of claim 27, wherein said preparing said primary composite material composition comprises orienting one or more material fibers of said primary composite material composition on a zero degree angle with respect to a longitudinal axis thereof, and wherein said preparing said supplemental composite material composition comprises orienting one or more material fibers of said supplemental composite material composition on a zero degree angle with respect to said longitudinal axis.
32. The method of claim 31, wherein said preparing said supplemental composite material composition comprises orienting a majority of material fibers of said supplemental composite material composition on a zero degree angle with respect to said longitudinal axis, and orienting a portion of said material fibers transverse to said longitudinal axis.
33. The method of claim 32, wherein said adapting further comprises operably securing together at least a portion of said material fibers of said primary composite material composition oriented on a zero degree angle with respect to said longitudinal axis with at least a portion of said material fibers of said supplemental composite material composition oriented transverse to said longitudinal axis.
34. The method of claim 27, further comprising optimizing said performance properties of said support member by strategically relating within said supplemental composite material composition a number and orientation of transverse material fibers to a number of material fibers oriented on a zero degree angle, each with respect to a longitudinal axis, and adapting these to reinforce a region of said primary composite material composition.
35. A method for providing a climbing structure, said method comprising:
- obtaining first and second composite support members, each having variable performance properties along a longitudinal length thereof provided by adapting a region of a primary composite material composition with a supplemental composite material composition to provide selective localized reinforcement of said primary composite material composition; and
- interconnecting said first and second composite support members to form at least a portion of said climbing structure.
Type: Application
Filed: Feb 16, 2007
Publication Date: Sep 6, 2007
Inventors: William Isham (Alpine, UT), Stephen Webber (Cedar Hills, UT)
Application Number: 11/707,642
International Classification: E06C 5/04 (20060101);